A current topic in the 3GPP RAN (Third Generation Partnership Project Radio Access Network) working groups is the mobility of UEs (User Equipments) between macro cells of eNBs (evolved NodeBs) and micro cells of HeNBs (Home evolved NodeBs). A User Equipment (UE) is expected to be in an area with radio coverage guaranteed by standard 3GPP LTE (Long Term Evolution) Macro-Cells (also referred to as macro radio cells in the following) served by eNBs and/or Micro-Cells (also referred to as micro radio cells in the following) served by HeNBs. Depending on various criteria, such as subscription type, user profile and so on, the UE may be allowed to access an HeNB or not. Furthermore, the UE may have certain other priorities, e.g., related to radio link quality, QoS, etc., on whether to prefer connections to a HeNB or a standard eNB.
The current status in 3GPP RAN working groups regarding the identification of macro radio cells served by eNBs and micro radio cells served by HeNBs is as follows:
The need for a method was identified to distinguish both types of mobile radio base stations (BS) such as e.g. eNB and HeNB in an early stage of the mobile radio cell acquisition procedure. One approach is the reservation of the available set of PCIs (Physical layer Cell Identities) for such micro radio cells (HeNBs). One alternative approach is the extension of the current set of available PCIs by providing additional primary synchronization signals (PSS) and to reserve this additional set of PCIs for micro radio cells. An open issue is whether the UE should be aware of the reserved set of PCIs for HeNBs or not.
In case that the UE is not aware of the reserved set of PCIs for HeNBs, the conventional solution requires that a UE synchronizes to an unknown BS (independent of whether it is an eNB or HeNB) and—in a second step—acquires and decodes the System Information (SI) of the mobile radio communication system in order to identify the type of the BS. The inherent process is relatively lengthy and the power requirements for performing all required steps may be high. This may have a direct impact on a variety of UE performance aspects, such as battery lifetime of the UE, and duration to perform handover from a macro cell (eNB) to a micro cell (HeNB) (cell type detection speed), which may lead to better QoS (Quality of Service) for the user at start-up (when UE is switched on) or during handover to another BS.
In order to extract the SI, the following broadcasting structure is to be taken into account: System Information (SI) is broadcast in the downlink transmission connection as an RRC (Radio Resource Control Protocol Layer) message carrying a number of System-Information-Blocks (SIBs) that have the same periodicity. Several SIBs have been defined including the so-called Master-Information-Block (MIB), that includes a limited number of most frequently transmitted parameters, and SIB Type 1 containing the scheduling information that mainly indicates when the other System Information (SI) RRC messages are transmitted, i.e. their start times.
SYSTEM INFORMATION MASTER (SI-M) and SYSTEM INFORMATION 1 (SI-1) are special versions of a System Information (SI) RRC message only carrying a single SIB, namely the MIB and the SIB Type 1, respectively. The SI-M message are carried on BCH (Broadcast Channel, one of the downlink transport channels) while all other System Information (SI) RRC messages including SI-1 are carried on DL-SCH (Downlink Shared Channel, another one of the downlink transport channels).
Both the SI-M and SI-1 use a fixed schedule with a periodicity of 40 ms and 80 ms, respectively. The first transmission of the SI-M is scheduled in radio frames for which the SFN mod 4=0. SI-1 is scheduled in radio frames for which the SFN mod 8=0. Moreover, SI-1 is scheduled in sub-frame #5. In this context, SFN is the mobile radio cell system frame number.
Furthermore and for reasons of completeness, it should be pointed out that the technique presented herein below is not related to the signaling of a “Neighbouring List”. A neighbouring list (also called “Neighbour Cell List”) gives specific identities of mobile radio base stations that are available in the neighbourhood and to which a communication connection is possible. This is unsuitable in the framework of the embodiments which will be described in the following, since the intention is to communicate a list of identities that are allocated to specific types of mobile radio base stations (BS) (e.g. HeNBs, standard eNBs, partially open HeNBs, etc.)—the signaling of the identities does not imply that the mobile radio base station of the corresponding identities are actually available. Typically, the ID range of a specific mobile radio base station type will be quite broad (e.g., 256 values among all available ones) while only a small number is actually deployed.